Email blacklist removal – How to stay off blacklists for uninterrupted mail service
Getting listed in a spam blacklist is a dreadful experience for server owners. Users end up facing email delivery failures and bounces, which can take your business reputation for a toss.
As a security measure, mail from blacklisted IPs are rejected by most mail servers. So, if you want uninterrupted mail services, you’ll need to stay clear of blacklists.
At Bobcares, our Dedicated Server Engineers help hundreds of businesses prevent IP blacklisting by blocking inbound and outbound spam. It involves 2 core activities:
1. 24/7 server monitoring
Our experts monitor critical server metrics such as disk usage and server processes round the clock. When we detect an anomaly in the mail logs, we immediately check and investigate for spamming, and prevent a blacklist.
2. Periodic audit and preventive maintenance
But waiting for an issue to happen, and jumping in to rescue is not the best way to keep a server stable. That is why we do regular Preventive Sever Maintenance.
Every coupe of weeks (or when there’s an abnormal spike in server metrics), we audit the server performance and security.
We check the server for security vulnerabilities, performance bottlenecks, hardware health issues, etc. and fix the issues, so that a server failure can be prevented.
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Email blacklists – How do servers get listed in email blacklists?
A spam blacklist is a database of IP addresses or hostnames of mail servers that are reported as sources of spam. If your mail server is listed in these blacklists, other mail servers will reject mails from your server.
These spam blacklists are often referred to as DNS-based Blackhole List (DNSBL) or Real-time Blackhole List (RBL). There are a number of Spam blacklists online, such as Spamhaus, Sorbs, Spamcop, etc.
Email blacklisting can usually occur in these scenarios.
- Your mail server gets compromised due to any malware or software vulnerabilities. Attackers can then hijack your mail server and send spam mails from it.
- Valid user accounts in your server send a bulk of emails to different email addresses, as a part of their business campaign or promotions or other event notifications.
- Email account passwords of users may get leaked to unauthorized users, who use these account to send bulk spam emails.
- Security loop holes in the mail server due to improper configuration and security patches can be exploited by spammers to send spam.
Email blacklist agencies keep track of the spamming server IP addresses using spam traps. Users can also submit complaints to the blacklisting agencies about spamming servers.
Examining the mail logs for email bounces and emails returning with a message such as ‘Sorry, you are sending from an IP that has been blacklisted.’, can reveal that your mail server is blacklisted.
Once your server IP address get blacklisted for spamming, getting it delisted is a time consuming process. Email service disruption for days or weeks can ruin your business.
That’s why its vital to protect your mail server from getting into a blacklist in the first place, and if at all it gets listed, timely detection and removal plays an important role.
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Email blacklist removal – How to go about it?
Constant monitoring of the mail server IPs in blacklists can be done using custom scripts. This is vital to detect and accomplish an email blacklist removal with minimal calamities.
If the mail server is blacklisted, immediate action we take is to stop the spamming and submit delist request after changing the mail server IP address.
Identifying the source of spamming is done by examining the email logs in the server. After pinpointing the culprit, immediate actions such as account suspension, disabling spamming scripts, etc. are done.
Mail server IP change helps to ensure seamless email delivery with the new IP address, if the previous one gets blacklisted, as delisting an IP address takes time, depending on the blacklisting agency.
We’ll discuss how to change mail interface IP in 3 popular mail servers.
1. How to change interface IP in Exim
If you are using exim mail server, it is easy to change the interface IP. The exim.conf file has to be checked for the section:
remote_smtp: driver = smtp
and under that, add the line:
interface = ip address
After updating the desired IP address, exim server has to be restarted:
service exim restart
To confirm the IP change, the exim log file and email headers should be examined.
2. How to change interface IP in SendMail
To change the mail server IP in Sendmail, the file to be edited is
/etc/mail/sendmail.mc. The following entry in the file has to be edited with the desired IP address in the ‘Addr’ section:
After editing, the new configuration file is generated using the
m4 macro processor:
m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
Restart Sendmail for the new update to take effect:
service sendmail restart
It is also possible to edit the configuration file sendmail.cf directly and make this change. But this is has to be done by experts, as it can end up breaking the mail server if not done right.
3. How to change interface IP in Postfix
The default configuration in Postfix makes the mail server available on all IP addresses. This is defined by the following entry in ” /etc/postfix/main.cf ” file:
inet_interfaces = all
To configure the Postfix mail server to listen to only a specified IP address, change the entry as follows:
inet_interfaces = IP_address
Restart the Postfix mail server and it would start sending the mails from the new IP address assigned.
systemctl restart postfix
Once the mail server IP is changed, the RDNS and other anti-spam lookup records have to be updated with the new IP address.
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